View Full Version : flushing a tankless water heter

06-14-2005, 09:25 AM
i have a tankless water heater from rinnai and was wondering on how to flush it. the instructions are vague and i think there are leaving out a few steps. any ideas?

master plumber mark
06-14-2005, 04:09 PM
if you figure out how to do it,
please let me know.....I have always wondered
how the hell it was supposed to be accomplished.

something to do with running vinegar through
the unit to get the lime out.....

I know if you install boiler drains (laundry hose faucets) on
both the inlet and outlet sides of the unit
with ball valves to isolate the unit , it makes it
pretty easy to flush the vinegar through the thing.

and then you are prepaired
for the next time it has to be done.

ya just gotta love high technology.

06-15-2005, 10:54 AM
This isn't going to help you with your problem but I have a question for you. How do you like your tankless water heater?
My old style water heater, 33 gallon is in need of replacement and I was thinking of going with a tankless. I have been to all the sites and have read all the propoganda (sp) but would like some input from an actual user.


06-15-2005, 08:01 PM
The volume they can supply is often limited, so if you are filling a tub, you may have to wait and you may have problems if you have two hot water taps running at the same time. They raise the temperature of the water a fairly fixed amount, depending on how cold your input water is in the end of the winter, it may not raise it to a decent comfort level. My inlet water temp at the end of the winter is barely above freezing. Most will raise the inlet water about 70 degrees, then add the loss of a long run of pipe, and you may have tepid water for a shower. It takes significant wattage to provide a large volume of water since it isn't in the device very long - you may have to upgrade your electrical service or live with a smaller volume of water. If using gas, you would need to provide combustion air, as a typical basement doesn't have enough air volume if you read the specs (for a decent sized heater - especially if you have a gas dryer and furnace (not direct vented) in the area). Many people ignore the volume requirement when determining if the thing will fit - they only look at its actual size and say it will fit where I want it. This can be a deadly mistake. Course, if you can see daylight through the foundation, it may not be an issue! The storage losses are way down, since there essentially isn't any, but if you get a well insullated storage tank, they may only drop a degree or so an hour, and you'll probably only have to replace it, never repair it. Don't expect the life or lack of maintenance or repairs to be the same on a tankless - they have more parts/sensors, and the heat exchanger gets less efficient as it ages. My unprofessional opinion. I'm going to replace my system this summer...

master plumber mark
06-15-2005, 09:42 PM
thats all that really can be said about tankless
units, they sound like a good idea,
but once the honeymoon
is over then the troubles start...

hereare some sites to real time data done by Bradford white
on both paths you can go down...

they sell both units so the tests were pretty fair.



06-16-2005, 09:29 AM
Master Plumber Mark and jadnashua, thanks for the input and also the links that you provided (I had seen the one but the Bradford White was new to me).

As I said I have read all or most of what I can find on this subject but I have not been able to communicate with anyone who has had any actual experience with one of these things.

Opinions seem to be divided into two very polarized camps, people either love them of hate them. But again most of these opinions are from those that don't use them.

I am leaning toward trying the tankless as there are just the two of us in the household and our hot water consumption is not that high. I will also go with the pilot less model which is a further savings.

Money considerations aside..........there is also the environmental aspect to this whole thing. Now I am not a tree hugger by any stretch of the imagination but I think that it is prudent to try and save some energy for our grandchildren down the road.

So I would still like to hear from Sly001 and your personal experience.


06-19-2005, 10:42 AM
hi there king,

if you haven't already, you might want to do a search using the forum search tool for the word 'tankless' and you'll find a number of opinions (including mine) about tankless h2o heaters.

not enough time to type mine out again right now, but if you check out my previous post on the subject i'm sure i was (as usual!) very chatty and opinionated!

in short, i love the Rinnai i'm using. i live in a cold climate and have no problems.

i don't have a houseful of water-users, but the folks i know up here with large families (inc. teenagers), lots of laundry, and even hot tubs to replenish have no problem with their Rinnai units.

that's all for now - whatever your choice, enjoy!


06-19-2005, 03:48 PM
Kavita, thanks............at last an opinion from someone who has some actual experience with these things. I haven't yet searched the posts but will do as soon as I get rid of all this family hanging around for fathers day.........LOL.

06-27-2005, 11:25 AM
[QUOTE=master plumber mark]"if you figure out how to do i know if you install boiler drains (laundrt,
please let me know.....I have always wondered
how the hell it was supposed to be accomplished.

something to do with running vinegar through
the unit to get the lime out....."

First of all, you start by installing a set of these on the heater:

Then you get one of these:

Now you're in business.